Field of the Invention
The present invention relates to a technical field of power electronics and, more particularly, to an isolating switch circuit and a control method thereof.
Description of the Related Art
Synchronous rectification is a method of using a power MOSFET with a relatively low on-resistance to replace a rectifier diode to reduce a rectification loss and is used in isolating switch circuits. The isolating switch circuit in the prior art generally includes a main power switch transistor, a transformer and a synchronous rectification transistor. The control circuit controls the turn-on state of the main power switch transistor, and the synchronous rectification control circuit controls a synchronous rectification transistor to realize the synchronous rectification. In an isolating switch circuit, an optical coupler is often adopted to realize transmission of primary and secondary feedback signals.
As shown in FIG. 1, a flyback switch circuit based on the synchronous rectification in the prior art is shown. A secondary signal is transmitted to the primary side through the optical coupler by sampling an output voltage of the secondary side and is received by a control circuit. The control circuit controls the action of the main power switch transistor correspondingly according to a feedback signal transmitted by the optical coupler. The optical coupler is used to achieve the signal transmission of the primary and secondary sides of the isolating switch circuit, although this can solve the problem of isolation, the technical problems of increasing the cost and enlarging the power consumption still exist. Further, the isolating switch circuit of the prior art based on the primary control has the technical problem of low precision.